The 50 g oral glucose tolerance test (OGTT), used to screen for gestational diabetes mellitus, has been administered without regard for the time of the last meal. We will measure the effect of prior feeding on blood glucose excursions following the 50 g OGTT in normal and diabetic pregnant women in the fasting and fed states. In order to understand the mechanism of any effect, serum insulin and C-peptide levels will also be determined.